FOR Rangers it was the perfect climax to an awkward, nervous night. For Kilmarnock, a sickening blow to the guts, their pain dulled only slightly by news of another league defeat for Dundee United.

Just when it seemed this exhausting fifth-round tie was destined to go the whole distance, into extra-time of tonight’s replay, sub Nicky Clark appeared from nowhere to glance a stunning volley high into the roof of Jamie MacDonald’s goal.

For long spells it felt as if this moment might never arrive, especially throughout a second-half slog that saw Kilmarnock’s players batten down the hatches in a torrential rain storm.

After handing Rangers an early lead with the hair-brained concession of a lightning quick penalty – and pulling level soon after – their defensive efforts were little short of gargantuan.

But in the end it all mattered for nothing as Clark got the run on them to fire Rangers into the quarter-finals where they will face either Dundee or Dumbarton.

Warburton arrived here in Ayrshire on a truly filthy night. As his team attempted to get a feel for the plastic beneath their feet, the rain was coming at them sideways and in icy sheets.

Martyn Waghorn celebrates after scoring (Image: SNS Group)

Kilmarnock bounced into this one off the back of a fairly monumental weekend win at Motherwell.

Accordingly, stand-in boss Lee McCulloch – taking the team for the last time – rolled out the same 11.

Manager in waiting Lee Clark stayed clear of the dugout, restricting himself to a watching brief in the main stand and wondering if he ought to trade in his new club car for something more practicable. Like an ark.

Clark may even have suspected he had arrived at his new club just in time for the end of days. Two minutes in it may well have felt like it as he watched Kilmarnock’s defence self-destruct to hand Rangers the early initiative.

There seemed no need for panic at first as Martyn Waghorn chased down a long probe over the top of Kilmarnock’s last line.

But the Geordie out muscled Stevie Smith as it skidded up off the surface and then came crashing to the ground with a thud after a tangle of legs.

It was basic stuff from Smith who was too sheepish to even contest the decision as referee Bobby Madden correctly pointed to the spot.

Rory McKenzie celebrates his equaliser (Image: SNS Group)

Waghorn got back to his feet to slam home from the spot, sending MacDonald the wrong way before signalling to the bench he was unable to continue any longer. And just like that, his night was over as Nicky Clark replaced him from the bench.

Lee Clark, on the other hand, was sitting uncomfortably in his seat. This was hardly the start he’d hoped for.

But if it felt as if all of Kilmarnock’s old frailties were about to be exposed there was another shock coming.

It arrived within five minutes as Rory McKenzie latched onto a loose ball midway inside the Rangers half and drove towards the penalty box.

Then 25 yards out he opted to let fly with a wicked, curling left-foot shot which picked up speed as it flashed past Wes Foderingham and fizzed inside the keeper’s right-hand post.

Soon after the rampaging Josh Magennis could have fired Kilmarnock in front had he not hesitated and allowed Rob Kiernan to slide into a last-gasp recovery tackle. Magennis came crashing down inside the box but Madden waved for play to continue.

Amid this gathering chaos Kilmarnock full-back Smith was the next groggy casualty to make way after failing to recover from a meaty collision, replaced by Lee Ashcroft as the action raged on around him. Half an hour in, Dominic Ball went into the book for clattering into the back of Greg Kiltie, turning the temperature up another notch and prompting an outburst from Warburton who earned a ticking off.

Lee Clark in the stands (Image: SNS Group)

There was a feeling, bubbling away never far under the surface, this contest was capable of exploding at any moment. It was that sort of night.

Had Kenny Miller aimed a little more carefully on the stroke of half-time, when he side-footed a shot across the face of goal after being set-up perfectly by Nicky Clark, then Rangers might finally have got on top of it.

But this tie was hanging in the balance as these two re-emerged for the second half.

It was break-neck stuff again, straight from the off but although this pair were now attempting to trade blows neither of them had the composure to craft a knock-out punch.

It was all too hectic, too harum scarum for cool heads to be kept at the vital moments although Rangers did come close twice with thumping long- range efforts from first Barrie McKay and then James Tavernier.

With an hour gone Warburton attempted to add a little precision and quality to these attacks by replacing the physical bulk of Ball with the quick- thinking craft of Dean Shiels.

Rangers' Nicky Clark makes it 2-1

Miller should have won a penalty when he was tugged on the shoulder inside the box by Ashcroft, just as he was threatening to pull the trigger.

But when Holt did let one rip soon after keeper MacDonald got down to his right to finger it around the base of his post. Rangers were ramping it up but Kilmarnock were furiously resisting.

Warburton made another change with Miller replaced by Harry Forrester. But the harder Rangers tried, the less likely they looked to break through.

With four minutes left it looked as if Forrester might finally be on the cusp as he stepped onto a bouncing ball deep inside Kilmarnock’s box.

The sub smashed his laces through it and blasted for goal only for Conrad Balatoni to throw his body on the line with a brave, flying block.

And then, deep into injury time, McKay fired a corner in from the left and Clark met it with a flashing volley at the front post to fire Rangers through with almost the last kick of the ball.